1. Field of the Invention
This invention relates to automotive suspension systems, and more particularly to a method and apparatus for controlling the displacement of a piston in a shock absorber.
2. Description of Related Art
Shock absorbers are used in connection with automotive suspension systems to absorb unwanted vibrations which occur during driving. To absorb this unwanted vibration, shock absorbers are generally connected between the body and the suspension of the automobile. A piston is located within the shock absorber and is connected to the body of the automobile through a piston rod. Because the piston is able to limit the flow of damping fluid within the working chamber of the shock absorber when the shock absorber is compressed or extended, the shock absorber is able to produce a damping force which counteracts the vibration which would otherwise be transmitted from the suspension of the automobile to the body.
When the wheel to which a shock absorber is associated encounters a steep drop in the road surface such as a pot hole, the piston would rise within the shock absorber housing to a point where the piston would contact the rod guide. Since the damping characteristics of the shock absorber often did not change as the piston approached the guide rod, the piston would often impact the rod guide at relatively high velocity. This high velocity impact of the piston with respect to the rod guide often had two detrimental effects with respect to vehicle cooperation. First, the impact between the piston and the rod guide would often cause ride discomfort as a result of the "jerk" that would be felt by the passengers when the piston encountered the rod guide. Further, the relatively high velocity impact of the piston with respect to the rod guide also increased the possibility that damage to the piston would occur which would require replacement of the shock absorber.